OBJECTIVES: Monotherapy with traditional mood stabilizers or atypical antipsychotics is recommended as the first-line treatment for pediatric bipolar disorder. This study examined the prescribing patterns of mood stabilizers and atypical antipsychotics and adherence to these medications in children and adolescents diagnosed with bipolar disorder. METHODS: 2003-2005 Medicaid Analytic eXtract data of four states namely California, Illinois, Texas and New York was used. Study participants were 6-18 years old, had a diagnosis of bipolar disorder, and had treatment initiation with atypical antipsychotic or mood stabilizer monotherapy after a 6 month window without filling any of these medications. Descriptive statistics was performed to observe the utilization pattern of monotherapy with mood stabilizers and atypical antipsychotics. Medication possession ratio (MPR) was compared between mood stabilizers and atypical antipsychotics during the 1 year period after the treatment initiation. RESULTS: Out of 62,858 patients diagnosed with bipolar disorder during the study period from 2003-05, there were a total of 14,946 patients who met inclusion criteria and whose treatment was initiated with mood stabilizer or atypical antipsychotic monotherapy. Prescription of atypical antipsychotics (73.36%) was predominantly higher than that of mood stabilizers (26.64%). Among the atypical antipsychotics, the most frequently prescribed medication was risperidone (30%) followed by quetiapine (18.2%) and olanzapine (14.4%). Among the mood stabilizers, the most frequently prescribed medication was oxcarbazepine (9.3%) followed by lithium (7.6% ) MPR for atypical antipsychotics was 0.82 ± 0.18 and that of mood stabilizers was 0.81 ± 0.19. Almost 65% of the patients initiated on either of the medications were fully adherent (MPR=1). CONCLUSIONS: After receiving the recent US FDA approval for the treatment of bipolar disorder in children and adolescents, atypical antipsychotics are prescribed more frequently than traditional mood stabilizers, especially in context of monotherapy. However, adherence to both the medication classes was similar.